1. Field of the Invention
The present invention relates to a an improved spray gun, of the syphon-cup type. More particularly, it relates to such a spray gun having a vented fluid supply container and means connected with the vent for preventing dripping of fluid therefrom upon use and movement of the gun.
2. The Prior Art
In the use of syphon-cup type paint spray guns, paint is syphoned through a tube from a supply container into an air stream, passing through the gun for discharge in a spray from an orifice in a nozzle of the gun. Since during spray the volume of paint within the container decreases, the container is vented to atmosphere to prevent a negative pressure from developing therein, with the resultant failure of paint to be syphoned into the gun. With such spray guns, paint within the container may pass through the vent and drip therefrom upon manipulation of the gun. Such dripping is not only undesirable, but is intolerable when it falls upon and mars an otherwise smooth, painted surface.
Various spray gun assemblies have been proposed to overcome this problem. For example, U.S. Pat. No. 4,174,070, granted to Lau et al, discloses an improved, syphon-type spray gun assembly including a spray gun and an associated supply container having a vent to atmosphere, which is characterized by means for preventing dripping from the assembly of contents of the container which pass through the vent. The means for preventing comprises a U-shaped tube, the first end of which communicates with the vent, and the second end of which is disposed in a position remote from the vent. While the device affords an improvement over a simple vent, dripping through the U-shaped tube can still occur, especially during tilting and shaking of the syphon cup to keep the paint in a thoroughly mixed state. This is often necessary between paint applications, since during the drying period when the paint spray assembly is not used, the paint may settle. Instead of using a mixing stick, which requires opening of the syphon cup, the operator will often simply place his thumb over the vent and shake the gun and cup to mix the paint. Upon release of the operator's thumb from the vent, gas build up will cause paint to squirt out of the vent.
U.S. Pat. No. 3,714,967, to Zupan et al, discloses a syphon paint spray cup assembly which provides an angularly-disposed, elongated vent passageway and reservoir in the cup cover to limit paint drip. However, the reservoir is not sufficient to contain the paint and prevent its dripping during shaking of the paint spray cup by the operator.
U.S. Pat. No. 4,405,088, to Gray, discloses an adaptor for syphon-type spray paint guns, which is provided with an internal- and external-type vent tube, however, once again, this device does not completely prevent dripping following shaking.
Finally, U.S. Pat. No. 4,832,232, to Broccoli, discloses a spray gun vent but for a pressure-type spray gun, which provides an external reservoir. However, the same does not allow for the paint to easily flow back into the container following venting and it is not intended for use with a syphon-type spray gun.